One of nature's oddest creatures has given up the secret of its incredible cancer immunity.The naked mole rat, a hairless rodent that lives in ant-like colonies underground, appears to enjoy complete protection against the disease, despite its unusually long 30-year lifespan. Now for the first time scientists believe they know why. The discovery could lead to exciting new cancer treatments for human patients.The key to the mole rat's freedom from cancer is a gooey substance in its body tissue that stops normal cells turning cancerous.Known as "high molecular weight hyaluronan", or HMW-HA, it surrounds mole rat cells and in the laboratory clogged up vacuum pumps and tubing. When the "goo" was taken away, cells became vulnerable to cancer triggers and started forming tumours.In the mole rat, HMW-HA's primary function is generating a very flexible, elastic skin that allows it to squeeze through narrow underground tunnels.Its rejuvenating effect on skin is already well known to the cosmetics industry, which uses it in anti-wrinkle creams and injections. This suggests HMW-HA could safely be used to treat cancer.Lead scientist Dr Andrei Seluanov, from the University of Rochester, US, said: "There's indirect evidence that HMW-HA would work in people. It's used in anti-wrinkle injections and to relieve pain from arthritis in knee joints, without any adverse effects. Our hope is that it can also induce an anti-cancer response."The naked mole rat's unique form of hyaluronan - part of the connective material between cells, or extracellular